What is Unagi ウナギ 【鰻】?
Unagi (ウナギ) is the Japanese word for the genus of freshwater eels and traditionally refers to the Japanese eel (jap. nihon-unagi). Unagi is a very popular ingredient in Japanese cuisine and is sold at a high price compared to other edible fish. In contrast to other fish species, the blood of the eel has a toxic effect and must therefore be heated sufficiently for consumption.
Unagi for Sushi and Sashimi
The mucous layer of the unagi can emit an unpleasant odour depending on the habitat and food. Therefore, both natural captive and farmed unagi are placed in clean water for one or two days before they are killed. The Japanese method of preparation of unagi follows several successive steps. First, the eel is cut open and filleted either at the head or on the ventral side, starting lengthwise. The meat is then cut into pieces of equal size, placed on skewers and gently roasted over charcoal. In the next step, the fillets are steamed and then dipped in sauce to be roasted again on the grill.
Unagi is rich in protein, vitamins and minerals. The cooked meat has an unmistakable taste which distinguishes it significantly from other fish. The prepared meat of unagi is very soft and fluffy, pleasant on the palate and usually without a fishy or earthy aftertaste. The high fat content gives it a full-bodied flavour, which can be enjoyed with a spicy soy-based sauce (jap. kabayaki) or sprinkled with salt alone (jap. shirayaki).
Occasionally the prepared meat from the unagi is sprinkled with Japanese pepper (jap. sansho, サンショウ) to give the meat a fresh smell. In addition, sansho is said to have a digestive effect which is supposed to support the absorption of the fatty unagi meat. For the preparation of unagi nigiri sushi, it is recommended to refrain from this and prefer sesame (jap. goma, ゴマ) or don't use any garnish at all.
Unagi Sauce (unagi no tare, うなぎのたれ)
Although unagi can be enjoyed without sauce (jap. tare), it is usually served with a thick broth specially prepared (jap. unagi no tare). At the time when the unagi sauce was not commercially produced in large quantities, it was considered an indication of the cook's skills. Nowadays, homemade unagi sauce is only to be found in high-quality or specialities restaurants.
The basic ingredients of unagi no tare are soy sauce, mirin, sugar and sake. Taste and consistency are similar to teriyaki sauce. Although unusual, the taste of the sauce is well suited as an addition to grilled meat dishes.
Unagi vs. Anago
Unagi is not considered a traditional ingredient for making sushi in Japan. Only rarely, or on advance order, you can find unagi as handmade nigiri in Japanese sushi restaurants (jap. sushi-ya, 寿司屋). More common is the use as an ingredient for pressed Sushi (oshi-zushi). In contrast, the conger eel (anago) is an essential part of the seasonal menu of a restaurant. Outside Japan, especially in North America and Europe, the situation is the opposite. Since Anago is rarely actively fished outside of Northeast Asia, it is simply too complicated or nearly impossible for most sushi chefs to obtain fresh Anago. Thus, mostly imported, frozen and (in the worst case) already industrially prepared unagi is used. Only in high-quality restaurants fresh and regionally available river eel is prepared.
Compared to anago, unagi is more tasty, fatty and meaty. Moreover, unagi is considered a higher quality delicacy in Japan and is therefore more expensive. In terms of taste, unagi differs from anago by its more intense and full-bodied taste. The common opinion is that anago, because of its lighter taste, harmonises better with soured sushi rice and is therefore the preferred choice for making sushi.
Although unagi is traditionally eaten on the “day of the ox” (jap. doyō no ushinohi), late autumn until early winter is considered the best season. During this time, the fishes build up fat reserves in order to draw on it during the winter, when they hibernate in holes and hollows.
Even though unagi is most tasty towards the beginning of winter, unagi is traditionally appreciated in the middle of summer. In Japan they say unagi gives you strength and endurance, which you need especially during the Japanese summer heat to prevent exhaustion.
Wild Capture vs. Aquaculture
Wild-caught unagi (天然ウナギ) has a lighter and less fatty taste than farmed unagi (養殖ウナギ). The meat is harder and the animals are said to be slightly larger. In contrast, aquacultured unagi lacks the smell of mud and soil, has a softer texture and a more consistent taste.
Even if purists prefer wild-caught unagi, it can generally be said that a predominant proportion of consumers consider aquaculture reared unagi more tasty and of higher quality. According to the Food and Agriculture Organisation of the United Nations (FAO), in 2018, approximately 97 % of the unagi production volume came from aquaculture.
Unagi in Japan
Archaeological excavations from the Jomon period testify that unagi was already used as a source of food in ancient times. During the expansion of Edo, unagi was considered the food of the common workers, which they caught during the draining of Tokyo Bay. Until the beginning of the Meji period, unagi was sold in mobile food stalls (jap. yatai, 屋台) along the roadside. Nowadays, unagi is mainly found in speciality restaurants.
Unagi on the Day of the Ox (土用の丑の日)
In Japan it is a custom to eat tasty unagi on the “day of the ox” (doyō no ushinohi), a celebration day that is repeated annually at the end of July. The origin of this custom is not clear, the theories range from the mention in poems, to the invention by a writer from the Kyōhō period, to the theory that the Japanese characters for ox (うし) resemble two eels.
In Japan, the term unagi nobori (うなぎのぼり), which can be freely translated as “climbing as an eel”, is similar to the expression “skyrocketing”. It means that the ascent or rise of something or someone progresses rapidly and is usually subject to special conditions and may only be temporary. The term is derived from the habit of unagi that after a certain time they return from the sea and hike up the mountain rivers to return to the ponds and lakes where they originally lived.
Unagi is a popular edible fish that has been fished in Japan and Europe for centuries and is valued as an ingredient. Growing consumer demand and the convergence of international trade flows in recent decades have increasingly contributed to its threat. The European eel is now considered to be in danger of extinction, while the Japanese and American eel, among others, are considered to be highly endangered. All species relevant as unagi are severely decimated in population size, although about 95 % of the consumed ungagi come from aquaculture, they are not bred in captivity. Instead, young eels (silver or glass eels) are taken from the wild and then reared in closed cultures and fattened until they are ready for slaughter.
Besides the excessive number of wild catches, the destruction of natural habitats, illegal fishing, and the fishing of juveniles for aquaculture poses an existential threat. Until the development of a so-called “complete aquaculture”, for which no glass eels have to be taken from the wild, a consumer must decide for himself to what extent each piece of unagi he orders affects the survival of the entire species.
The common practice is to raise juvenile eels (glass eels) from wild stocks in aquaculture. It is still not possible to breed commercially viable unagi in captivity. Artificially fertilised eggs and successful hatching have been repeatedly achieved under laboratory conditions. Research continues to face serious problems in terms of food supply, resource consumption and the need for hormonal feminisation of the spawn.
Characteristics & Ecology
Freshwater eels (jap. unagi-ka) are aquatic and live in a variety of habitats, including freshwater, estuaries and marine areas. They spend most of their lives in rivers and migrate to the sea to breed.
The members of the unagi family have an elongated cylindrical body and many species reach a length of one meter. The largest species, the giant mottled eel (ōunagi), can reach a total length of up to two metres. Unagi are predominantly nocturnal predatory fish whose prey includes small fish, worms, crabs and also snails.
The economically most important species can be found in the following table.
|Japanese name||Common name||Endangerment (IUCN)|
|Giant mottled eel
Many fish belonging to the freshwater eel family (jap. unagi-ka) are considered commercially important seafood. In the last decade, the increase in industrial aquaculture breeding has shown enormous growth rates, with the largest production centres being located in East Asia.